It says a study presented at a major climate science conference in Denmark has predicted that one-third of its trees will be killed by even modest temperature rises.

The research, by some of Britain’s leading experts on climate change, shows that even severe cuts in deforestation and carbon emissions will fail to save the emblematic South American jungle, the destruction of which has become a powerful symbol of human impact on the planet.

Up to 85% of the forest could be lost if spiralling greenhouse gas emissions are not brought under control, the experts said.

But even under the most optimistic climate change scenarios, the destruction of large parts of the forest is “irreversible”.

Vicky Pope, of the Met Office’s Hadley Centre, which carried out the study, said: “The impacts of climate change on the Amazon are much worse than we thought.

“As temperatures rise quickly over the coming century, the damage to the forest won’t be obvious straight away but we could be storing up trouble for the future.”

He said: “When I was young I thought chopping down the trees would destroy the forest, but now it seems that climate change will deliver the killer blow.”

The study, which has been submitted to the journal Nature Geoscience, used computer models to investigate how the Amazon would respond to future temperature rises.

It found that a 2C (3.6F) rise above pre-industrial levels, widely considered the best case global warming scenario and the target for ambitious international plans to curb emissions, would still see 20-40% of the Amazon die off within 100 years.

A 3C (5.4F) rise would see 75% of the forest destroyed by drought over the following century, while a 4C (7.2F) rise would kill 85%.

“The forest as we know it would effectively be gone,” Dr Pope said.

Experts had previously predicted that global warming could cause significant “die-back” of the Amazon.